Negotiators for Yale and its unions reached an agreement on the use of casual and temporary workers Tuesday, resolving one of the major issues of contention between the two sides during the two-month negotiation process.

The agreement, considered tentative until final contracts are settled, calls for stricter monitoring of the use of temporary employees, who perform clerical and technical work but are not covered under union contracts and do not receive benefits or pensions. The agreement would also convert at least 40 positions currently held by casual and temporary workers into bargaining unit jobs, giving the workers filling those positions benefits and representation by the union.

The job security agreement represents a major advancement in the progress toward new contracts for locals 34 and 35, which represent Yale’s clerical, technical, service and maintenance workers. Union leaders described job security as among their chief concerns when negotiations began in February, and Tuesday’s resolution of part of the job security issues in Local 34 follows a major settlement on job security for Local 35 two weeks ago.

University leaders said they consider Tuesday’s agreement a major step toward finalizing contracts, and said they are hopeful that the contracts can be settled by the end of May. But with other major issues still on the table — including wages and benefits, as well as further discussion of Local 34 job security — union leaders said it is too early to say when contracts might be done.

“My sense is that we’ve now resolved for both 34 and 35 what really ought to be the most fundamental non-economic issue, apart from wages and benefits, so I’m very pleased,” Yale President Richard Levin said.

But union leaders cautioned that Tuesday’s settlement, while a major step toward reaching contracts, still left many more issues to be discussed.

“It’s a very important issue, but it’s only a part of the whole question of Local 34 job security,” union spokeswoman Deborah Chernoff said. “It’s an important piece of that but it’s still a piece.”

Negotiators have yet to discuss wages or benefits. Union leaders have also said they want to address the organizing efforts of graduate students and hospital workers as part of the current negotiations, something University officials say they will not discuss at the bargaining table.